MF多源测深数据融合方法及大洋水深模型构建

针对全球深海测深数据来源复杂、精度差异大、难以融合构建高精度数字水深模型(digital bathymetric model,DBM)的问题,提出一种适用于深水区多源水深数据融合的MF法(merge-fusion),并将其应用到马里亚纳海沟"挑战者深渊"的DBM构建中。该方法通过"合并-融合"的技术路线,将多波束、单波束、电子海图数据与通用全球海洋地形数据(general bathymetric chart of the oceans,GEBCO)有机地融合在一起,在保留高分辨率地形细节特征的同时,合理填补了数据空白区。使用该方法构建"挑战者深渊"高精度DBM并与GEBCO数据进行对比,结果表明,该方法融合的DBM能更好地反映精细的地形特征信息,具有重要的实际应用价值。     

An Evaluation of Publicly Available Global Bathymetry Grids

We evaluate the strengths and weaknesses of six publicly available global bathymetry grids: DBDB2 (Digital Bathymetric Data Base; an ongoing project of the Naval Research Laboratory), ETOPO2 (Earth Topography; National Geophysical Data Center, 2001, ETOPO2 Global 2’ Elevations [CD-ROM]. Boulder, Colorado, USA: U.S. Department of Commerce, National Oceanic and Atmospheric Administration), GEBCO (General Bathymetric Charts of the Oceans; British Oceanographic Data Centre, 2003, Centenary Edition of the GEBCO Digital Atlas [CD-ROM] Published on behalf of the Intergovernmental Oceanographic Commission and the International Hydrographic Organization Liverpool, UK), GINA (Geographic Information Network of Alaska; Lindquist et al., 2004), Smith and Sandwell (1997), and S2004 (Smith, unpublished). The Smith and Sandwell grid, derived from satellite altimetry and ship data combined, provides high resolution mapping of the seafloor, even in remote regions. DBDB2, ETOPO2, GINA, and S2004 merge additional datasets with the Smith and Sandwell grid; but moving from a pixel to grid registration attenuates short wavelengths (<20 km) in the ETOPO2 and DBDB2 solutions. Short wavelengths in the GINA grid are also attenuated, but the cause is not known. ETOPO2 anomalies are offset to the northeast, due to a misregistration in both latitude and longitude. The GEBCO grid is interpolated from 500 m contours that were digitized from paper charts at 1:10 million scale, so it is artificially smooth; yet new efforts have captured additional information from shallow water contours on navigational charts. The S2004 grid merges the Smith and Sandwell grid with GEBCO over shallow depths and polar regions, and so is intended to capture the best of both products. Our evaluation makes the choice of which bathymetry grid to use a more informed one. The U.S. government right to retain a non-exclusive royalty-free license in and to any copyright is acknowledged.     

Along-track gravity anomalies from Geostat and Seasat altimetry: GEBCO overlays

To provide easy access to the large number of Seastat and Geosat altimeter observations collected over the last decade, we have plotted these satellite altimeter profiles as overlays to the General Bathymetric Chart of the Oceans (GEBCO). Each of the 32 overlays displays along-track gravity anomalies for either ascending (southeast to northwest) or descending (northeast to southwest) altimeter passes. Where Seasat and Geosat profiles coincide, only the more accurate Geosat profiles were plotted. In poorly charted southern ocean areas, satellite altimeter profiles reveal many previously undetected features of the seafloor.     

含碎石层沥青加铺结构外部耦合计算方法

碎石化沥青加铺路面结构中不同层位材料性质差异显著,难以由同一种力学模型加以描述。针对这一问题,将沥青加铺层及碎石化混凝土视为连续及非连续颗粒介质,分别采用有限差分法(DEM)与颗粒离散单元法(PCC)模拟沥青加铺层及碎石结构层的力学行为,并采用耦合的方式,通过两域对应边界的相容条件与平衡条件的控制,实现了连续域与离散域的平滑过渡。作为应用,结合现场情况,将破碎混凝土简化成碎粒层、碎石表层和碎石底层,通过模拟计算,分析了破碎粒径不同组合条件下沥青加铺层对荷载的响应。结果表明,碎粒层粒径越大,沥青层的拉应力、应变越大;碎石表层粒径越小,即多锤头破碎机(MHB)破碎的越碎,原水泥混凝土面板的强度下降的越多,整体性就越差,沥青层底的拉应力、应变也就越大,因此要将破碎状态控制在一定程度为宜。     

Disbond detection with piezoelectric wafer active sensors in RC structures strengthened with FRP composite overlays

The capability of embedded piezoelectric wafer active sensors (PWAS) to perform in-situ nondestructive evaluation (NDE) for structural health monitoring (SHM) of reinforced concrete (RC) structures strengthened with fiber reinforced polymer (FRP) composite overlays is explored. First, the disbond detection method were developed on coupon specimens consisting of concrete blocks covered with an FRP composite layer. It was found that the prescnce of a disbond crack drastically changes the electromecbanical (E/M) impedance spectrum measured at the PWAS terminals. The spectral changes depend on the distance between the PWAS and the crack tip. Second, large scale experiments were conducted on a RC beam strengthened with carbon fiber reinforced polymer (CFRP) composite overlay. The beam was subject to an acccleratcd fatigue load regime in a three-point bending configuration up to a total of807,415 cycles. During these fatigue tests, the CFRP overlay experienced disbonding beginning at about 500,000 cycles. The PWAS were able to detect the disbonding before it could be reliably seen by visual inspection. Good correlation between the PWAS readings and the position and extent of disbond damage was observed. These preliminary results demonstrate the potential of PWAS technology for SHM of RC structures strengthened with FRP composite ovcrlays.     

一种高效的多波束全覆盖测量工作量估算方法

利用Surfer软件强大的土方量计算功能,及其Scripter模块的编程功能,结合大洋水深图(GEBCO)的水深数据,实现了全自动估算多波束全覆盖测量野外工作量的方法,旨在为相关测量单位进行工作量估算时提供参考与帮助。最后通过对多个工区的历史测量数据进行验证,采用本方法获得的工作量与实际工作量的平均误差为4%左右,取得了满意的效果。